Radiotelegraphy



' L. F. FULLER.

RADIOTELEGRAPHY.

APPLICATION FILED MAY 21, 1917.

1,336,833 Patented Apr- 13, 1920 INVENTOR L. F FULLEF? Witness ///5 A TTORNEY6 UNITED STATES PATENT OFFICE.

LEONARD F. FULLER, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO FEDERAL TELEGRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALIFORNIA.

RADIOTELEGRAPHY.

Specification of Letters Patent.

Patented Apr. 13, 1920.

T 0 all whom it may concern:

Be it known that I, LEONARD F. FULLER, a citizen of the United States, and a resident of the city and county of San Francisco and State of California, have invented certain new and useful Improvements in Radiotelegraphy, of which the following is a specification.

The invention relates to radio telegraphy and particularly to an arc radio transmitter including a generator of the Poulsen type.

An object of the invention is to produce an arc radio transmitter of less cost, size and weight for a given power capacity than has been heretofore accomplished.

Another object of the invention is ,to provide an arc radio transmitter, the D. C. generator of which is safer to handle than the generators in prior transmitters.

The Poulsen arc radio generator comprises a closed chamber containing an atmosphere of hydrogen in which are'arranged electrodes between which the arc is formed. The are gap is subjected to a strong transverse magnetic field produced by field windings arranged in the direct current circuit which supplies the arc. A choke coil is arranged in each arm of the circuit between the direct current generator and the arc to prevent the high frequency oscillations produced by the are from reaching the generator. For purposes of coil insulation it has always been considered essential to place the magnet windings in the lead, between the generator and the are electrode which is grounded. In this prior construction it is inadvisable to ground the frame of the D. C. generator on account of the large inductive kick of the arc magnet winding, which produces dangerous potential surges which, if the frame were grounded, would be impressed on the D. C. generator insulation, causing burn-outs. The generator frame has, therefor, been insulated from earth, with the result that it frequently became highly charged and therefore a source of danger. Also, in the tropics the material used for insulating the frame from earth sometimes "warps and. shrinks, throwing the generator out of alinement with the prime mover. I have found that by combining the choke and magnet coils and placing them in the lead which is connected to the antenna side of the are and by grounding the other side of the generator armature and the generator frame, that a better and cheaper construction is produced than was possible with the prior arrangement. Usually, but not necessarily, the negative lead is connected to the ground ed side of the arc.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description, where I shall outline in full that form of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings, I have shown one specific embodiment of my invention, but it is to be understoodv that the invention as expressed in the claims may be embodied in a plurality of forms.

Referring to said drawings:

Figure 1 is a diagrammatic representation of my invention.

Fig. 2 is a diagrammatic representation of a modified form of arc generator.

Fig. 3 is an elevation, half in section, of the combined magnet and choke coils.

The oscillation generator of my invention comprises the two electrodes 2-3, between which the arc is formed, the electrode 2 being connected preferably to the positive side of the electric generator 4 and to the antenna 5 and the electrode 3 being connected preferably to the negative side of the generator 4 and to ground. The magnetizing winding 8 is arranged in the lead between the generator 4 and the electrode 2. The winding 8 may be concentrated on one pole or may be placed on both poles and when so placed the windings may be in series, as shown in Fig. 2, or may be in parallel. The other lead connects the grounded electrode 3 directly with the armature 9, and this side of the armature and the generator frame 12 are grounded.

I have found it to be of great advantage to combine the magnet winding and the choke coil in one winding. That end of the combined winding which is connected to the electrode 2 is constructed to serve as the choke coil and since it is often impossible to determine in advance which end of the coil will be connected to the electrode, on account of various features of installation, I prefer to form choke coils 14-15 at each end of the combined coil. The turns of the winding nearest the electrode are subjected to higher duty than the inner turns of the coil and the outer turns 14 and 15 are, therefore, more heavily insulated than the inner turns. The end turns on both ends of the coil are covered with increased insulation for the reason stated before, but when it is definitely known which end of the coil is to be connected to the electrode, the turns on that end only will be provided with the heavier insulation.

The combined coil is built up on a spool 16 within which the magnet pole is arranged and the windings are spaced from the flanges 17 of the spool and are provided within themselves with annular passages 18 which serve as air ducts for ventilating and cooling the windings. The ducts communicate with the spaces between the windings and the flanges 17, thereby permitting a free circulation of air around and through all parts of thewinding, which consists of a plurality of annular sections spaced apart by air passages.

This construction produces a more compact transmitting unit than prior constructions, thereby possessing the advantage of occupying smaller space, a feature which is of advantage on ship board, where space is usually at a premium. Also, this construction reduces the number of parts thereby reducing the number of spare parts which must be carried in stock, a feature of im portance to the Navy.

I claim:

In a radio telegraph transmission system, a direct current generator having a grounded frame and an armaturegrounded on one side, two electrodes between which an arc is formed, one electrode being connected to the ungrounded side of the armature and the other to the grounded side of the armature, an antenna circuit connected to the electrode on the ungrounded side, a magnet pole arranged adjacent the gap between the electrodes, a choke coil connected to the ungrounded electrode and surrounding the pole and a magnetizing winding surrounding the pole and connected to the choke coil and to the ungrounded side of the armature.

In testimon whereof, I have hereunto set my hand at an Francisco, California, this 15th day of May 1917.

LEONARD F. FULLER.

In presence of- H. G. P122031. 

